NAME

       namespace.conf - the namespace configuration file

DESCRIPTION

       The pam_namespace.so module allows setup of private namespaces with polyinstantiated directories.
       Directories can be polyinstantiated based on user name or, in the case of SELinux, user name, sensitivity
       level or complete security context. If an executable script /etc/security/namespace.init exists, it is
       used to initialize the namespace every time an instance directory is set up and mounted. The script
       receives the polyinstantiated directory path and the instance directory path as its arguments. The script
       is invoked with full root privileges and accessing the instance directory in this context needs to be
       done with caution, as it is controlled by the unprivileged user for which it has been created.

       The /etc/security/namespace.conf file specifies which directories are polyinstantiated, how they are
       polyinstantiated, how instance directories would be named, and any users for whom polyinstantiation would
       not be performed.

       When someone logs in, the file namespace.conf is scanned. Comments are marked by # characters. Each non
       comment line represents one polyinstantiated directory. The fields are separated by spaces but can be
       quoted by " characters also escape sequences \b, \n, and \t are recognized. The fields are as follows:

       polydir instance_prefix method list_of_uids

       The first field, polydir, is the absolute pathname of the directory to polyinstantiate. The special
       string $HOME is replaced with the user's home directory, and $USER with the username. This field cannot
       be blank.

       The second field, instance_prefix is the string prefix used to build the pathname for the instantiation
       of <polydir>. The path must end in a trailing slash, or in a directory prefix used to build the full
       per-instance path. Depending on the polyinstantiation method it is then appended with "instance
       differentiation string" to generate the final instance directory path. This directory is created if it
       did not exist already, and is then bind mounted on the <polydir> to provide an instance of <polydir>
       based on the <method> column. The special string $HOME is replaced with the user's home directory, and
       $USER with the username. This field cannot be blank.

       The third field, method, is the method used for polyinstantiation. It can take these values; "user" for
       polyinstantiation based on user name, "level" for polyinstantiation based on process MLS level and user
       name, "context" for polyinstantiation based on process security context and user name, "tmpfs" for
       mounting tmpfs filesystem as an instance dir, and "tmpdir" for creating temporary directory as an
       instance dir which is removed when the user's session is closed. Methods "context" and "level" are only
       available with SELinux. This field cannot be blank.

       The fourth field, list_of_uids, is a comma separated list of user names for whom the polyinstantiation is
       not performed. If left blank, polyinstantiation will be performed for all users. If the list is preceded
       with a single "~" character, polyinstantiation is performed only for users in the list.

       The method field can contain also following optional flags separated by : characters.

       create=mode,owner,group - create the polyinstantiated directory. The mode, owner and group parameters are
       optional. The default for mode is determined by umask, the default owner is the user whose session is
       opened, the default group is the primary group of the user.

       iscript=path - path to the instance directory init script. The base directory for relative paths is
       /etc/security/namespace.d.

       noinit - instance directory init script will not be executed.

       shared - the instance directories for "context" and "level" methods will not contain the user name and
       will be shared among all users.

       mntopts=value - value of this flag is passed to the mount call when the tmpfs mount is done. It allows
       for example the specification of the maximum size of the tmpfs instance that is created by the mount
       call. In addition to options specified in the tmpfs(5) manual the nosuid, noexec, and nodev flags can be
       used to respectively disable setuid bit effect, disable running executables, and disable devices to be
       interpreted on the mounted tmpfs filesystem.

       The directory where polyinstantiated instances are to be created, must exist and must have, by default,
       the mode of 0000. The requirement that the instance parent be of mode 0000 can be overridden with the
       command line option ignore_instance_parent_mode

       In case of context or level polyinstantiation the SELinux context which is used for polyinstantiation is
       the context used for executing a new process as obtained by getexeccon. This context must be set by the
       calling application or pam_selinux.so module. If this context is not set the polyinstantiation will be
       based just on user name.

       The "instance differentiation string" is <user name> for "user" method and <user name>_<raw directory
       context> for "context" and "level" methods. If the whole string is too long the end of it is replaced
       with md5sum of itself. Also when command line option gen_hash is used the whole string is replaced with
       md5sum of itself.

EXAMPLES

       These are some example lines which might be specified in /etc/security/namespace.conf.

                 # The following three lines will polyinstantiate /tmp,
                 # /var/tmp and user's home directories. /tmp and /var/tmp
                 # will be polyinstantiated based on the security level
                 # as well as user name, whereas home directory will be
                 # polyinstantiated based on the full security context and user name.
                 # Polyinstantiation will not be performed for user root
                 # and adm for directories /tmp and /var/tmp, whereas home
                 # directories will be polyinstantiated for all users.
                 #
                 # Note that instance directories do not have to reside inside
                 # the polyinstantiated directory. In the examples below,
                 # instances of /tmp will be created in /tmp-inst directory,
                 # where as instances of /var/tmp and users home directories
                 # will reside within the directories that are being
                 # polyinstantiated.
                 #
                 /tmp     /tmp-inst/               level      root,adm
                 /var/tmp /var/tmp/tmp-inst/        level      root,adm
                 $HOME    $HOME/$USER.inst/inst- context

       For the <service>s you need polyinstantiation (login for example) put the following line in
       /etc/pam.d/<service> as the last line for session group:

       session required pam_namespace.so [arguments]

       This module also depends on pam_selinux.so setting the context.

SEE ALSO

       pam_namespace(8), pam.d(5), pam(7)

AUTHORS

       The namespace.conf manual page was written by Janak Desai <janak@us.ibm.com>. More features added by
       Tomas Mraz <tmraz@redhat.com>.

Linux-PAM                                          09/06/2025                                  NAMESPACE.CONF(5)